1. Field of the Invention
The present invention relates to a medical image processing device for capturing and displaying a medical image of an observation target inside a subject under inspection, and a method for operating the medical image processing device.
2. Description Related to the Prior Art
Recently, in diagnosing stomach cancer, it has been recognized that the onset of the stomach cancer is closely related to the presence of Helicobacter pylori (H. pylori). In 1994, WHO (the World Health Organization) announced that the H. pylori is a carcinogen. The eradication of the H. Pylori infection has been performed to prevent the stomach cancer. After the eradication, whether the eradication has been successful is examined.
Whether a patient is infected or uninfected with the H. pylori is examined by a blood test or by using an endoscope system including a light source device, an endoscope, and a processor device. In the endoscope system, illumination light is applied from the endoscope to an observation target. Based on RGB image signals, which are obtained by capturing an image of the illuminated observation target with an image sensor of the endoscope, an image of the observation target is displayed on a monitor. In the case where diffuse redness appears in the image on the monitor, it is diagnosed that there is a high possibility of the presence of the H. pylori and it is likely to cause cancer. It is also known that the presence of the H. pylori correlates with IHb (also referred to as the hemoglobin index, which is represented by a G/R ratio between a G image signal and an R image signal) (see Japanese Patent Laid-Open Publication No. 2003-220019). In Japanese Patent Laid-Open Publication No. 2003-220019, the IHb is used as an index for determining whether the eradication of the H. pylori infection has been successful. According to Japanese Patent Laid-Open Publication No. 2003-220019, in the case where the IHb is greater than a threshold value “59”, it is diagnosed that the eradication of the H. pylori infection has not been successful and the H. pylori is still present. In contrast, in the case where the IHb is less than the threshold value “59”, it is diagnosed that the H. pylori infection has been eradicated successfully.
As illustrated in FIG. 44, in a feature space formed by the B/G ratio (the vertical axis, the ratio between the B image signal and the G image signal) and the G/R ratio (horizontal axis), the coordinates corresponding to a portion of the observation target uninfected with the H. pylori are distributed in an observation area “A”. The coordinates corresponding to a portion of the observation target infected with the H. pylori are distributed in an observation area “B”. The coordinates corresponding to a portion of the observation target in which the eradication of the H. pylori infection has been successful are distributed in an observation area “C”. In this feature space, the observation areas “A” and “B” are completely apart from each other. In this case, the observation areas “A” and “B” are distinguished from each other based only on the value of the G/R ratio (the horizontal axis), that is, the value of the IHb. On the other hand, the observation area “B” and the observation area “C” are mixed in the feature space, so that it is difficult to distinguish the observation area “B” from the observation area “C” based only on the value of the G/R ratio (the horizontal axis). Therefore, it has been required to display images which allow distinction, using a method other than that using the IHb, between the portion infected with the H. pylori and the portion in which the eradication of the H. pylori infection has been successful.